Well, I'm writing you to get some advice in which graphic card could I buy this Christmas.

1.Gaming Limits.

Well, gaming limits... games like Assassin's Creed 2 (to come I guess), Darkest of Days, CoD 6... at highest graphical quality, 1680x1050, DX10 (and even DX11 I guess). I also want, desperately, to play games like Empire: Total War fluently at its highest quality, with all quality settings at highest; and obviously to use NVidia Physx at High level (setting that did Darkest of Days go hellishly slow even with lowest settings; thing which changed when I disabled Physx: it went smoothly with highest settings).

2.Budget.

I'd be able to spend around 300-400€, which in $ would be... 450-600$, but if it can be cheaper, it'd be much better XD.

3.Power supply.

230V.

4.Computer specs.

Processor: Intel Core 2 Quad Q8200 @ 2.33GHz.
Motherboard: Benicia 1.01.
Graphic interface: PCI-Express
Memory: DDR2, 4096 MBytes.
Graphics:
GPU: NVIDIA GeForce 9600 GS.
Clocks: Core 500MHz, Shaders 1250MHz, Memory 500MHz
Memory: 768 MBytes DDR2, Bus Width 192 bits.
DX11 (it says so in DXDiag).

5.Country.

I'm from Barcelona, Spain.


Well, I hope you can give me some advice, thanks in advance and have a nice day !

The voltage of your system is not too helpful. What we need is the wattage of your current power supply, brand, and model.

HI! Like raybay said you need a powerful supply, and as a video card you can buy two of them and put them on parallel, of course if you have two slots for video. this will let you to play any game you want. A second choice is that your new graphic card should have at least 256 bits. I hope I was helpful and I apologize for my bad english.

You will likely need a new powersupply, probably a CORSAIR CMPSU-750TX 750W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply - Retail
paired with a SAPPHIRE 100282SR Radeon HD 5850 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card w/ATI Eyefinity - Retail.

I suggest the Corsair 650TX instead of the 750. The HD 5850 should be a great way forward.

Yeah your probably right. I guessed at the 750.

For the graphics card, i suggest you the HD 5850, that can max everything in 1680x1050.
Probably you'll need a better power supply, I suggest the Corsair VX550, or HX520, if you want go modular.